vim-patch:8.1.2380: using old C style comments

Problem:    Using old C style comments.
Solution:   Use // comments where appropriate.
306139005c

src/nvim/ex_docmd.c

@@ -7494,7 +7494,7 @@ static void ex_syncbind(exarg_T *eap)
 
       ctrl_o[0] = Ctrl_O;
       ctrl_o[1] = 0;
-      ins_typebuf(ctrl_o, REMAP_NONE, 0, TRUE, FALSE);
+      ins_typebuf(ctrl_o, REMAP_NONE, 0, true, false);
     }
   }
 }